A Package Technology for Miniaturized Field-Effect Transistor-Based Biosensors and the Sensor Array

Abstract

In this study, a package technology has been developed for miniaturized filed-effect transistor (FET)-based biosensors. FETs were fabricated and diced as a 1 mm × 1 mm chip. The chip was then embedded in a plastic substrate and has a coplanar surface with that of the substrate. Photolithography followed by metal deposition and lift-off process was conducted to create metal lines, which connect the FET and extend to the edge of the plastic substrate. The FET-embedded plastic substrate was then engraved by laser to form a typical micro SD card and then passivated by photoresist, leaving the source-drain channel and the gate electrode open, followed by bonding a microfluidic channel made of PMMA. The packaged FET was tested in air and in buffer solution to confirm the well electrical isolation between metal interconnects and the solution, and the successful liquid flowing in the microfluidic channel. A FET sensor array was also made by embedding 8 FET chips into one plastic substrate with the same process. This package technology can largely reduce the cost of the sensor due to the very small size of the FET chip. The sensor chips can also be arbitrarily positioned into one plastic substrate to fit with multiple microfluidic channels, leading to great flexibility in the design of the sensor array. The result has shown a promising 2D system-in-package technology for sensor applications.